Those skilled in the art are well aware of the technological importance of chelating agents for removing metal ions from various effluents, such as waste water, plating baths and the like. Chelating agents provide means of manipulating and controlling metal ions by forming complexes that usually have properties that are markedly different from those of the original metal ions or the chelators. These properties may serve to reduce undesirable effects of metal ions in drinking water, waste water, sewage and the like. Thus, new and improved chelating agents are continuously being developed which have a high selectivity and capacity for binding various metal ions.
An important class of chelating agents are those which are derived from a bis-imidazolyl moiety. These compounds have shown an excellent ability to bind various metal ions, especially Cu.sup.2+, effectively due to the proximity of the lone electron pairs on each of the nitrogen atoms in the imidazolyl rings.
Extensive studies of various bis-imidazolyl compounds have been conducted in recent years to determine the binding characteristics of these compounds, See, for example Drey, et al. "Metal Chelates of Bis-Imidazole," Biochemistry, Vol. 4, No. 7, pp. 1258-1263, July 1965 and Breslow, et al., "Models or Metal Binding Sites in Zinc Enzymes. Synthesis of Tris [4(s)-imidazolyl]carbinol (4-TIC), Tris (2-imidazolyl)carbinol (2-TIC), and Related Ligands, and Studies on Metal Complex Binding Constants and Spectrum," JACS, Vol. 100, No. 12, pp. 3918-3922, June 1978.
A specific bis-imidazolyl compound that has been developed in recent years is disclosed in U.S. Pat. No. 4,869,838 to Gorun et al. More specifically, the reference discloses a bis-imidazole ether of the following formula: ##STR2## wherein R is a normal alkyl group having from 1 to 12 carbon atoms and R' is a normal alkyl group having from 7 to 12 carbon atoms, an alkylaryl group having from 7 to 20 carbon atoms, or an aryl group of 6 to 10 carbon atoms. The above-identified bis-imidazolyl ether compounds are useful for complexing metal ions which are present in lubricating oils.
Despite the current state of the art, there is still a need for developing new metal chelators that have the ability to selectively and reversible bind metal ions. Additionally, due to the growing awareness of the environment in recent years, there is a continual need for developing new metal chelators that have the capacity for binding large quantities of trace amounts of metal ions from various effluent streams.